PTT signalling using Soundcard/DSP drivers

There seems to be some confusion on how drive PTT with my Soundcard and DSP driver. So here are some instructions on how to do it

SoundBlaster and Compatible drivers

• Serial Port
• Parallel Port
• Vox circuitry

WindowsSoundSystem (WSS) and Compatible drivers

• Serial Port
• Parallel Port
• Game Port
• Vox circuitry

Personal Sound Architecture (PSA) Soundcards

• Game Port
• Vox circuitry
• Using the FLAG_OUT pin of the DSP chip (see ADACOM Magazine #6)

Texas Instruments TMS320C26 and TMS320C50 DSP Starters Kits (DSK)

• Serial Port
• Vox circuitry

DG1SCR DSP Board

• Serial Port
• Vox circuitry
• The Board's PTT outputs

Analog Devices EZKIT Lite

• Vox circuitry
• Using the PFx output pins of the board

The Parallel Port Solution

The Serial Port Solution

The Game Port Solution

The Vox Circuitry

Please note that the Vox circuitry should only be used for 1200 baud AFSK. It is not well suited for 9600 baud FSK

You must adjust the output level of the right channel to the highest possible volume in order to have enough signal voltage to turn on the MOSFET transistor.

Note: Instead of a BC237, most general purpose small signal NPN transistors may be used as well, such as the BC547 or 2N2222.